1. Field of the Invention
The present invention relates in general to a television receiver (TV) which is capable of receiving a quadrature-modulated video signal, and more particularly to an apparatus and a method for enhancing a transient edge of a video signal, in which spark noises are detected from the video signal and then removed, so that a high picture quality can be obtained.
2. Description of the Prior Art
Generally, to obtain a distinct picture in an EDTV or a HDTV, there has been proposed an apparatus for enhancing a transient edge of a video signal One example of this form of apparatus is shown in a block form in FIG. 1, herein.
As shown in FIG. 1, the conventional apparatus for enhancing the transient edge of the video signal comprises delays 1 and 2 for sequentially delaying the video signal input ted therein, amplifiers 3 to 5 for amplifying the original video signal and the video signals delayed by the delays 1 and 2, respectively, an adder 6 for adding output signals from the amplifiers 3 to 5, an attenuator 7 for adjusting a level of an output signal from the adder 6, a delay 8 for delaying the output signal from the delay 1 to match a transmission time thereof with that of an output signal from the attenuator 7, and an adder 9 for adding an output signal from the delay 8 to the output signal from the attenuator 7 and outputting the added signal as the video signal, the transient edge of which is finally enhanced.
The operation of the conventional transient edge enhancement apparatus with the above-mentioned construction will hereinafter be described.
Upon inputting the video signal, the inputted video signal is sequentially delayed by a predetermined time period by the delays 1 and 2. Noticeably, the inputted video signal is enhanced vertically if the delay time of the delays 1 and 2 is a period of one line, while horizontally if the delay time is a period of one sample.
The amplifier 3 amplifies the inputted video signal and then applies the amplified video signal to the adder 6. Also, the video signals sequentially delayed by the delays 1 and 2 are amplified by the amplifies 4 and 5, respectively, and then applied to the adder 6. The output signals from the amplifiers 3 to 5 are added by the adder 6. As a result, the transient edge of the video signal is enhanced by the adder 6.
The output signal from the adder 6 is level-adjusted by the attenuator 7 and then added by the adder 9 to the output signal from the delay 8. As a result, the transient edge of the video signal is finally enhanced by the adder 9.
FIG. 2 is a waveform diagram illustrating a general video signal, FIG. 3 is a waveform diagram illustrating the video signal in FIG. 2 in which the transient edge is enhanced by the conventional transient edge enhancement apparatus and FIG. 4 is a waveform diagram illustrating a human visual characteristic with respect to the enhanced transient edge in FIG. 3.
As mentioned above, the conventional transient edge enhancement apparatus is adapted to enhance the transient edge of the video signal, more particularly luminance and color signals separated from the video signal However, as shown in FIG. 3, in the conventional transient edge enhancement apparatus, the transient edge of the video signal is enhanced together with an over shoot and an under shoot contained therein as shown in FIG. 2. This results in an unnaturalness in a picture quality.
Also, as shown in FIG. 3, in the conventional transient edge enhancement apparatus, the transient edge of the video signal is enhanced together with spark noises A and B contained in the video signal as shown in FIG. 2. This results in a degradation in the picture quality Further, the enhancement on the transient edge is performed regardless of a width of the transient edge. As a result, a high picture quality cannot be obtained because the transient edge is enhanced regardless of different frequency bands of input video signals in various systems such as, for example, a VCR, a HDTV, an EDTV, S-VHS and the like.